In the construction of many fluid handling devices, such as flowmeters and flow controllers, it is often critically necessary that the reliability of such sealing mechanisms be maintained under very adverse conditions, for example high temperatures, vacuum conditions of outer space, and conditions involving the passage of highly corrosive gaseous fluids. Such requirements make it undesirable to use conventional non-metal seals such as rubber gaskets and this has given rise to a variety of completely metal vacuum sealing devices, such as using metal O-ring seals, knife edge seals with flat metal gaskets, and the like. The metal vacuum joint described in Carlson et al U.S. Pat. No. 3,208,758 is one approach to the problem in which soft, flat metal gasket is penetrated by annular ridges. However, there are a number of problems that are not solved by such prior metal gasket seals. For example, because the glands themselves are intended to be reused with the replacement of the metal seal, a portion or all of the ridge on one of the glands can become duller than the other with the result that only one side of the gasket may be effectively penetrated. This may compromise the effectiveness of the seal in allowing leakage of fluid past the dull edges, building a "dead volume" of trapped fluid which can then contaminate for subsequent fluid flow. Some means, therefore, is desired to assure that there will be even penetration by the ridges even though one of the ridge surfaces is duller than the other. It would also be desirable to be able to use metal for the gasket, such as nickel, that does not out-gas upon baking and which is impervious to most environments. Nickel, being harder than usual copper metal gaskets, requires that the system design be particularly capable of uniformly and repeatedly applying penetrating forces to the opposing surfaces of the gasket.
In addition, it would be desirable to have the gland design capable of accommodating a variety of other seals so that a single gland design can be utilized to interface with a variety of different devices having varying requirements. For example, it would be desirable to utilize the same gland design to accommodate less demanding seals, such as a rubber O-ring while still providing the advantages of low dead volume and reproducibility. In some cases, it may even be desirable to weld a component to the port defined by the gland and a design which would accommodate, and facilitate, such welding would be highly desirable.
The present invention provides a sealing device having the foregoing desired attributes. A leak-tight seal is formed by sandwiching a rigid but malleable gasket such as a metal or teflon gasket between opposing annular ridges surrounding the port to be sealed. Reproducibility and assurance of proper seating of the annular gland ridges are assured by using a metal gasket design that cooperates with mating surfaces of the gland. In particular, the metal gasket is formed as an annular disk with a central opening and with an annular flange thicker than the disk integral with the disk, and extending vertically from both sides. The flange is disposed in grooves in the gland defined by the piercing ridges and wall structure of the glands and associated free, base surface of the glands. The design is such that it can be used to seal joints with standard rubber O-rings and its structure is such, in particular embodiments, to facilitate welding at the port which it defines, if that is desired.
In the preferred embodiment, in which a flanged metal gasket is sandwiched between opposing glands, a highly effective, reliable sealing device is provided which can withstand adverse temperatures and harsh fluid environments. Because of the particular mating structure between the gland geometry and that of the gasket flange, it is not necessary to have highly polished facing surfaces, as is sometimes the case with prior art mechanisms. The result is an inexpensive, serviceable, easy-to-machine and use device capable of sealing under the most adverse of conditions.
The gland can have a variety of configurations serving not only to surround and seal off a port, but also as a mechanism for sealing within a bore. In one embodiment, complementary glands are disposed in opposed confronting relationship, each gland defining a groove by an annular wall on one side and an annular ridge on the other side of a free, base surface of the gland. The ridge terminates in a sharp edge for piercing the gasket while the groove houses the flange of the gasket. The gasket is an annular disk with a central opening, the flange being located on its circumference as a thickened portion with opposite horizontal surfaces for seating on corresponding flat surfaces of the gland base which lies between the annular ridge and wall.
In another embodiment, the gasket has its flange adjacent the opening. In this embodiment, one of the glands is formed with an opening centrally therethrough while the other is formed with a threaded shank that extends through the opening. A jam nut can be used to progressively close the glands together, not only piercing and securing the metal gasket, but causing the edges of the gasket to extend horizontally outwardly to thereby seal a bore in which the glands are located.
The gasket for the present invention is unique, comprising an annular disk formed with a central vertical opening and with an annular flange thicker than the disk, integral with an edge of the disk. In one particular embodiment, the flange is disposed on the circumference of the disk. In another embodiment, the flange is disposed at the central opening of the disk. The flange extends equally from both sides of the disk and is formed on each side with flat horizontal surfaces.